Simultaneous carbon reutilization for primary sludge and stable nitrite production in a hydrolytic acidification...

Partial denitrification (PD, nitrate → nitrite) is a promising process for the hazardous nitrate removal by producing nitrite for Anammox. In this study, the startup and performance of PD using slowly biodegradable organic matter in primary sludge was explored by combining with in-situ hydrolytic acidification (HA). Results showed that efficient PD was established with 61.3% nitrite production at an influent nitrate level of 50 mg/L, with a simultaneous 23.1% reduction in volatile sludge mass. Efficient electron donors including acetate (13.2%), dissolved saccharide (11.9%), and intracellular poly-hydroxyalkanoates (22.5%) were generated from sludge HA, jointly promoting desirable nitrite production. Microbial analysis revealed that adding primary sludge significantly increased community diversity; however, the specific genera Dechloromonas (11.9%) and Thauera (10.5%) remained stably enriched to facilitate the efficient sludge reduction and nitrite production. These findings provide a novel strategy for simultaneously treating primary sludge, nitrate contaminant, and domestic wastewater using a HAPD and Anammox process.